Revert "[MBP] Reduce code size by running tail merging in MBP."

This reverts commit r271930, r271915, r271923.  They break a thumb selfhosting
bot.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@272017 91177308-0d34-0410-b5e6-96231b3b80d8
6 files changed